Trucks and trailers loaded with cargo and products move across the country to deliver products to commercial loading and unloading docks at stores, warehouses, and distribution centers. Trucks can have a trailer mounted on the truck, or can be of a tractor-semi trailer configuration. To lower overhead costs at retail stores, in-store product counts have been reduced, and products-in-transit now count as part of available store stock. Unloading trucks quickly at the unloading docks of warehouses and regional distribution centers has attained new prominence as a way to refill depleted stock.
Trucks are typically loaded and unloaded with forklifts if the loads are palletized and with manual labor if the products are stacked within the trucks. Unloading large truck shipments manually with human laborers can be physically difficult, and can be costly due to the time and labor involved. In addition, hot or cold conditions within a confined space of a truck trailer or shipping container can be deemed unpleasant work. Consequently, a need exists for an improved unloading system that can unload bulk quantities of stacked cases and cargo from truck trailers more quickly than human laborers and at a reduced cost.
In order to be economical, automation of loading or unloading needs to be relatively fast. Generally-known approaches to unloading cartons quickly have had extremely limited acceptance. It has been proposed to unload trailers without specific knowledge of exact locations of cartons within the trailer by applying bulk handling techniques. For example, the entire trailer can be tipped to move product toward a rear end door. For another example, cartons are placed on fabric layer that is pulled toward the rear end door to dump the contents. In both instances, integrity of packaging and contents of cartons are jeopardized by applying bulk handling techniques. At another extreme, it is known to use an articulated robotic arm with a machine vision sensor on an end effector that scans a scene focused on an area of next position for a pick or put. Extensive imaging processing and 3D point cloud processing occurs in an attempt to detect cartons that are present within in a narrow portion of the carton pile. The wait time between operations makes it difficult to achieve an economical return on investment (ROI) for an automated trailer loader or unloader. Even with extensive detection efforts, failures to detect individual cartons occur due to difficulty to sense edges that are too tightly aligned for 3D detection or otherwise too optically camouflaged for 2D detection.